package com.pubinfo.passbook.common.utils;

import lombok.extern.slf4j.Slf4j;

import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Base64;
import java.util.Random;

@Slf4j
public class Pbkdf2Sha256 {
  
  /**
   * 盐的长度
   */
  public static final int SALT_BYTE_SIZE = 16;
  
  /**
   * 生成密文的长度(例：64 * 4，密文长度为64)
   */
  public static final int HASH_BIT_SIZE = 64 * 4;
  
  /**
   * 迭代次数(默认迭代次数为 2000)
   */
  private static final Integer DEFAULT_ITERATIONS = 24000;
  
  /**
   * 算法名称
   */
  private static final String algorithm = "pbkdf2_sha256";
  
  /**
   * 获取密文
   *
   * @param password   密码明文
   * @param salt       加盐
   * @param iterations 迭代次数
   * @return
   */
  public static String getEncodedHash(String password, String salt, int iterations) {
    SecretKeyFactory keyFactory = null;
    try {
      keyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
    } catch (NoSuchAlgorithmException e) {
      log.error("Could NOT retrieve PBKDF2WithHmacSHA256 algorithm", e);
    }
    KeySpec keySpec = new PBEKeySpec(password.toCharArray(),
        salt.getBytes(StandardCharsets.UTF_8), iterations, HASH_BIT_SIZE);
    SecretKey secret = null;
    try {
      secret = keyFactory.generateSecret(keySpec);
    } catch (InvalidKeySpecException e) {
      log.error("Could NOT generate secret key", e);
    }
    
    //使用Base64进行转码密文
    byte[] rawHash = secret.getEncoded();
    byte[] hashBase64 = Base64.getEncoder().encode(rawHash);
    return new String(hashBase64);
    
    //使用十六进制密文
//        return toHex(secret.getEncoded());
  }
  
  /**
   * 十六进制字符串转二进制字符串
   *
   * @param hex 十六进制字符串
   * @return
   */
  private static byte[] fromHex(String hex) {
    byte[] binary = new byte[hex.length() / 2];
    for (int i = 0; i < binary.length; i++) {
      binary[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16);
    }
    return binary;
  }
  
  /**
   * 二进制字符串转十六进制字符串
   *
   * @param array 二进制数组
   * @return
   */
  private static String toHex(byte[] array) {
    BigInteger bi = new BigInteger(1, array);
    String hex = bi.toString(16);
    int paddingLength = (array.length * 2) - hex.length();
    if (paddingLength > 0) {
      
      return String.format("%0" + paddingLength + "d", 0) + hex;
    }
    
    return hex;
    
  }
  
  /**
   * 密文加盐     (获取‘SALT_BYTE_SIZE’长度的盐值)
   *
   * @return
   */
  public static String getsalt() {
    //盐值使用ASCII表的数字加大小写字母组成
    int length = SALT_BYTE_SIZE;
    Random rand = new Random();
    char[] rs = new char[length];
    for (int i = 0; i < length; i++) {
      int t = rand.nextInt(3);
      if (t == 0) {
        rs[i] = (char) (rand.nextInt(10) + 48);
      } else if (t == 1) {
        rs[i] = (char) (rand.nextInt(26) + 65);
      } else {
        rs[i] = (char) (rand.nextInt(26) + 97);
      }
    }
    return new String(rs);
  }
  
  /**
   * 获取密文
   * 默认迭代次数：2000
   *
   * @param password 明文密码
   * @return
   */
  public static String encode(String password) {
    return encode(password, getsalt());
  }
  
  /**
   * 获取密文
   *
   * @param password   明文密码
   * @param iterations 迭代次数
   * @return
   */
  public static String encode(String password, int iterations) {
    return encode(password, getsalt(), iterations);
  }
  
  /**
   * 获取密文
   * 默认迭代次数：2000
   *
   * @param password 明文密码
   * @param salt     盐值
   * @return
   */
  public static String encode(String password, String salt) {
    return encode(password, salt, DEFAULT_ITERATIONS);
  }
  
  /**
   * 最终返回的整串密文
   * <p>
   * 注：此方法返回密文字符串组成：算法名称+迭代次数+盐值+密文
   * 不需要的直接用getEncodedHash方法返回的密文
   *
   * @param password   密码明文
   * @param salt       加盐
   * @param iterations 迭代次数
   * @return
   */
  public static String encode(String password, String salt, int iterations) {
    // returns hashed password, along with algorithm, number of iterations and salt
    String hash = getEncodedHash(password, salt, iterations);
    return String.format("%s$%d$%s$%s", algorithm, iterations, salt, hash);
  }
  
  /**
   * 验证密码
   *
   * @param password       明文
   * @param hashedPassword 密文
   * @return
   */
//  public static boolean verificationHash(Object password, String hashedPassword, String salt) {
//    //hashedPassword = 算法名称+迭代次数+盐值+密文;
//    SimpleHash sh = new SimpleHash(
//        "MD5",//algorithmName加密算法
//        password,//source 被加密的对象
//        salt, //salt 盐值
//        1);//hashIterations 加密
//
//    return hashedPassword.equals(sh.toHex());
//  }
  
  /**
   * 验证密码
   *
   * @param password       明文
   * @param hashedPassword 密文
   * @return
   */
  public static boolean verification(String password, String hashedPassword) {
    //hashedPassword = 算法名称+迭代次数+盐值+密文;
    String[] parts = hashedPassword.split("\\$");
    if (parts.length != 4) {
      return false;
    }
    //解析得到迭代次数和盐值进行盐值
    Integer iterations = Integer.parseInt(parts[1]);
    String salt = parts[2];
    String hash = encode(password, salt, iterations);
    return hash.equals(hashedPassword);
  }
}
